A system, method and program product for enhancing dose uniformity during ion implantation are disclosed. The present invention is directed to allowing the use of an at least partially untuned ion beam to obtain a uniform implant by scanning the beam in multiple rotationally-fixed orientations (scan directions) of the target at variable or non-uniform scan velocities. The non-uniform scan velocities are dictated by a scan velocity profile that is generated based on the ion beam profile and/or the scan direction. The beam can be of any size, shape or tuning. A platen holding a wafer is rotated to a new desired rotationally-fixed orientation after a scan, and a subsequent scan occurs at the same scan velocity profile or a different scan velocity profile. Also included is a method, system and program product for conducting a uniform dose ion implantation in which the target is rotated and tilted about greater than one axes relative to the ion beam.
Legal claims defining the scope of protection, as filed with the USPTO.
1. A method for conducting uniform dose ion implantation of a target with an ion beam, the method comprising the steps of: providing an ion beam; determining an ion beam profile of the ion beam; determining a scan velocity profile based on the ion beam profile, the scan velocity profile dictating a non-uniform scan velocity across the target to provide a uniform dose; tilting the target about a first tilt axis and a second tilt axis such that the target is angled relative to the ion beam; rotating the target about a location substantially at a center of the target; implanting the target using the ion beam including varying a scan velocity according to the scan velocity profile; and repeating the rotating step and the implanting step.
2. The method of claim 1 , wherein the ion beam profile determining step includes measuring the ion beam using a multi-pixel Faraday detector.
3. The method of claim 1 , wherein the ion beam is at least partially un-tuned.
4. The method of claim 1 , wherein the ion beam profile includes a current density.
5. The method of claim 1 , wherein the scan velocity profile determining step includes: identifying a starting scan velocity profile; computing a dose on the target at each position for the scan velocity profile combined with the ion beam profile, and computing a standard deviation of the dose; determining whether the standard deviation meets a target criterion; in the case that the standard deviation meets the target criterion, proceeding with the implanting step, otherwise determining whether a number of allowed attempts to find a satisfactory scan velocity profile has been exceeded; and in the case that the number of allowed attempts has been exceeded, indicating an error, otherwise computing a new scan velocity profile.
6. The method of claim 5 , further comprising the step of determining whether the new scan velocity profile is acceptable and corralling the new scan velocity profile if the new scan velocity profile is unacceptable.
7. The method of claim 6 , further comprising the step of repeating the scan velocity determining step in the case that the new scan velocity profile is corralled or acceptable.
8. The method of claim 5 , wherein the new scan velocity profile computing step includes one of making a systematic modification of the starting scan velocity profile, and computing a multi-dimensional search algorithm.
9. The method of claim 1 , wherein the first tilt axis extends substantially perpendicular to the second tilt axis, and an axis of rotation is substantially parallel to the ion beam.
10. An apparatus for conducting uniform dose ion implantation of a target with an ion beam, the apparatus comprising: a source of an ion beam for implanting the target, the ion beam having an ion beam profile; a target scan translator configured to move the target through the ion beam according to a scan velocity profile that is based on the ion beam profile, the scan velocity profile dictating a non-uniform scan velocity across the target; a target tilter configured to tilt the target about at least two axes; a target rotator configured to rotate the target about a location substantially at a center of the target; and a processor configured to operate the target scan translator, the target tilter and the target rotator to provide a substantially uniform dose of ions across the target.
11. The apparatus of claim 10 , wherein the target rotator rotates the target from a rotationally fixed orientation to a subsequent rotationally-fixed orientation between at least two implanting scans, and wherein the processor further operates to determine whether to change the scan velocity profile after the target rotator rotates the target to the subsequent rotationally-fixed orientation.
12. The apparatus of claim 11 , wherein the scan velocity profile is also based on the rotationally-fixed orientation of the target.
13. The apparatus of claim 10 , further comprising a multi-pixel Faraday detector to determine the ion beam profile.
14. The apparatus of claim 10 , further comprising means for determining the scan velocity profile including: means for identifying a starting scan velocity profile; means for computing a dose on the target at each position for the scan velocity profile combined with the ion beam profile, and computing a standard deviation of the dose; means for determining whether the standard deviation meets a target criterion; means for determining whether a number of allowed attempts to find a satisfactory scan velocity profile has been exceeded in the case that the standard deviation does not meet the target criterion, and otherwise proceeding with implanting; and means for computing a new scan velocity profile in the case that the number of allowed attempts has not been exceeded, and otherwise indicating an error.
15. The apparatus of claim 14 , further comprising means for determining whether the new scan velocity profile is acceptable and corralling the new scan velocity profile if the new scan velocity profile is unacceptable.
16. The apparatus of claim 14 , wherein the new scan velocity profile computing means includes one of: means for making a systematic modification of the starting scan velocity profile, and means for computing a multi-dimensional search algorithm.
17. A computer program product comprising a computer useable medium having computer readable program code embodied therein for controlling an ion implanter system to provide a substantially uniform dose to a target, the ion implanter system including a target translator configured to move the target through the ion beam, a target tilter configured to tilt the target relative to the ion beam about greater than one axis and a target rotator configured to rotate the target about a location substantially at a center of the target, the program product comprising: program code configured to determine an ion beam profile of the ion beam; program code configured to determine a scan velocity profile based on the ion beam profile, the scan velocity profile dictating a non-uniform scan velocity across the target to be used by the target translator to provide a substantially uniform dose to the target; and program code configured to determine whether to tilt the target about more than one axis to provide a substantially uniform dose to the target.
18. The program product of claim 17 , wherein the scan velocity profile determining code includes: program code configured to identify a starting scan velocity profile; program code configured to compute a dose on the target at each position for the scan velocity profile combined with the ion beam profile, and computing a standard deviation of the dose; program code configured to determine whether the standard deviation meets a target criterion; program code configured to determine whether a number of allowed attempts to find a satisfactory scan velocity profile has been exceeded in the case that the standard deviation does not meet the target criterion, and otherwise proceed with implanting; and program code configured to compute a new scan velocity profile in the case that the number of allowed attempts has not been exceeded, and otherwise indicate an error.
19. The program product of claim 18 , further comprising program code configured to determine whether the new scan velocity profile is acceptable and corrall the new scan velocity profile if the new scan velocity profile is unacceptable.
20. The program product of claim 17 , wherein the new scan velocity profile computing code includes one of: program code configured to make a systematic modification of the starting scan velocity profile, and program code configured to compute a multi-dimensional search algorithm.
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December 23, 2004
January 23, 2007
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